Vulture aerodynamics
 

Foster the vulture was captured yesterday having curiously decided to escape from captivity to Essex.

Foster is very ugly, but he looks like he has very good aerodynamics. What is the purpose/benefit/effect of the way in which his relatively high aspect ratio wings divide at the tips into several smaller spanwise winglets? Do we have anything to learn from him?

A more efficient implementation of wingtip sails.. reduces induced drag in a manner similar to increasing the span ...

I thought their purpose was almost certainly to minimise induced drag. If they are "more efficient" than, say, winglets or fences, what aspect of their design makes them unsuitable for use on man made aircraft? Slow operating speed of vultures? Overcomplexity of making them all independently controllable (presuming that a vulture has this facility)?

They reduce induced drag by providing a net forward force using the upwash off the wingtip. The feathers are angled downwards into the upwash and the net force therefore has a forward component. It's been tried with a fair anount of success in tunnel tests (Sorry, I don't know where/when). I'm amazed that everybody doesn't have them now.

Come to think of it, there's an interesting picture of an experimental aircraft on page 19 of "Today's Pilot" magazine (July) that appears to use a combination of fences and wing tip sails. It's worth a look.

Pie

[This message has been edited by Pielander (edited 25 June 2001).]

Pielander is spot on. For those looking for an indepth analysis, read the Feb 1988, "The Aeronautical Journal", article "Wing tip sails: Progress to date" by JJ Spillman.

grob103

Voltures also utilise a unique method to lighten the load when utilising evasive manuevers- they regurgitate. Nothing worse than a load of putrid pre-digested carion on the windscreen to make ones day.